Catalytic cracking process



United States Patent Office 3,542,668 Patented Nov. 24, 1970 U.S. Cl. 208-67 3 Claims ABSTRACT OF THE DISCLOSURE A normally gaseous olefin, and particularly butene-l, is charged with the hydrocarbon oil feed to a catalytic cracking operation to increase the yield of unsaturates therefrom for higher quality alkylate production.

BACKGROUND OF THE INVENTION This invention relates to the catalytic conversion of hydrocarbons of relatively high molecular weight into hydrocarbon products of lower boiling molecular weight and boiling range. In accordance with a further aspect, this invention relates to the introduction and admixing with a hydrocarbon oil charged to a catalytic cracking operation an octane improving amount of a normally gaseous olefin prior to contact with hot catalyst. In accordance with a still further aspect, this invention relates to admixing a high purity butene-l stream with a hydrocarbon oil feed charged to a catalytic cracking zone using a silica-alumina catalyst to maximize butene-Z production for production of high octane alkylate and with a minimum loss of butenes to cracking or hydrogen.

Catalytic cracking processes of many types are well known in the art and have been widely practiced for a long time in the petroleum industry, particularly for the production of motor fuel range hydrocarbons from heavier hydrocarbon oils, mostly in the gas oil or higher boiling ranges. These processes normally employ such catalysts as various natural or treated clays, various composites of silica gel with alumina, magnesia and/or boria, activated alumina, activated carbon, etc., at temperatures of about 700-1100 F., pressures ranging from subatmospheric to several hundred atmospheres, and widely varying feed rates in fixed bed, moving bed, fluid catalyst, or a suspensoid operation, specific conditions depending upon the character of the feed and the products desired.

There are continuing efforts by the petroleum industry to improve the product characteristics and properties so as to render various processes, and particularly catalytic cracking processes, more economical. For example, the industry is continually working to improve the octane value of the gasoline products produced. In the present state of development in which the country is looking for ways of reducing smog and other atmospheric pollutants, it appears that the elimination of much of the lead content of gasolines may be in the offering. The increase in octane number of gasoline produced which would require no, or only a small amount of, octane improvement chemicals (potential atmospheric contaminants) would be of considerable advantage.

In accordance with the invention, it has been found that the octane number of gasoline products produced from catalytic cracking operations can be substantially increased by introducing and admixing with the hydrocarbon oil charged to the cracking process an octane improving amount of a normally gaseous olefin such as butene-l.

Accordingly, an object of this invention is to provide an improved process for the conversion of hydrocarbon oils to more valuable products such as gasolines.

An object of this invention is to improve the octane quality of the gasolines produced from catalytic cracking operations.

A further object of this invention is to provide a commercially feasible method for improving catalytic cracking operations to produce high quality gasoline products.

Other aspects, objects, and the several advantages of the invention will be apparent to those skilled in the art upon further study of the specification and the appended c aims.

SUMMARY OF THE INVENTION In accordance with the invention, normally gaseous olefins and hydrocarbon feed oils are mixed and then charged to a catalytic cracking zone to maximize olefin production for production of high octane alkylate with a minimum loss of olefins to cracking or hydrogenation.

In accordance with one embodiment of the invention, a high purity butene-l and gas oil are admixed prior to contacting with the catalyst and then charged, together, to a catalytic cracking zone using silica-alumina catalyst to maximize butene-Z production for production of high octane alkylate with a minimum loss of butenes to cracking or hydrogenation.

It has been found that by mixing the light normally gaseous hydrocarbons with the hydrocarbon feed oil prior to contacting with the catalyst, the admixture prevents undue cracking of the gaseous feed and also results in a considerable increase in octane number, e.g., a four octane number increase, of the material when alkylated.

The amount of normally gaseous olefin, and especially butene-l, added to the hydrocarbon oil charged to the catalytic cracking zone will range from 0.1 to 18.0 weight percent "of the oil feed. The amount of butene-l, for example, admixed with the hydrocarbon oil feed will often range from 0.05 to 15.0 weight percent, particularly when a high purity butene stream is admixed with the hydrocarbon oil charged to the catalytic cracking zone.

The catalytic cracking operation of the invention can be carried out at temperatures ranging from about 800 F. to about 1100 F., pressures of from about 0 to about p.s.i.g., and liquid feed rates of about 0.2 to 5.0 volumes per volume of catalyst per hour.

Conventional catalytic cracking feedstock such as paraflinic, naphthenic, or mixed base gas oils, or heavier hydrocarbon oils such as reduced crudes, topped crudes, or the like, can be used according to the invention for the production of high octane motor fuels. The invention is particularly applicable to hydrocarbon feed oils higher boiling than gasoline, which normally boil above about 600 F.

While all types of conventional cracking catalysts mentioned above can be employed, silica-alumina catalysts are preferred. Catalysts used in the process can comprise acid treated bentonite and synthetic silica-alumina catalysts which are stable at high temperatures of the order of 1300 F. to 1600 F. and which are substantially free from alkali and alkaline earth metals. A satisfactory catalyst is a synthetic silica-alumina catalyst containing about 86.5 to 87.0 percent SiO and about 12.5 to 13.0 percent Al O The process of the invention can be carried out in fixed bed, moving bed, fluid catalyst or suspensoid operation, as will be readily understood by those skilled in the art.

EXAMPLE The process of the invention can be applied to the production of motor fuels from gas oil range or higher boiling conventional cracking feedstocks as follows.

A gas oil boiling in the range of about 650 to 1200" F. is introduced into a fluid catalytic cracking zone containing a silica-alumina catalyst maintained at a temperature 3 in the range of 890 to 950 F., preferably 900 to 920 F. at substantially atmospheric pressure. The catalyst to oil weight ratio is maintained within the range of about 1:1 to 8:1 depending upon the conversion desired, normally about 4: 1.

A high purity butene-l stream (85-95 percent butene- 1) is introduced into and admixed with the gas oil prior to introduction into the cracking zone. The butene-l stream is introduced into the gas oil feed stream at a rate of 10 to 200 cubic feet per barrel of gas oil feed.

The product from the cracking operation charging the added butene-l is distilled into a gaseous fraction, a gasoline out and a bottoms cut comprising unconverted gas oil. A portion of the gas oil stream recovered can be recycled to the catalytic cracking operation. A butylenes fraction recovered from the gaseous fraction can be subsequently alkylated to produce an alkylate product having a Research Octane Number with 3 cc. TEL of 107.5.

Similarly, the butylenes fraction recovered from the gaseous fraction obtained from a catalytic cracking operation not utilizing butene-l introduced into the gas oil feed stream, but having the same quantity of butene-l added to the butylenes fraction recovered from the catalytic cracking operation, is charged to alkylation, the produced alkylate having a Research Octane Number with 3 cc. TEL of 106.8.

Since the added butene-l in the examples is about ten percent of the total butylenes charged to alkylation, the increase in octane is 0.7 unit when operating in accordance with the invention as compared to the prior operation. With a greater quantity of outside butene-l processed, the octane increase is greater.

Both catalytic cracking conditions (temperatures, pressures, catalyst, etc.) are the same in each example. Both alkylation operations comprise conventional HF catalytic alkylation of isobutane with the butylenes using the same operating conditions.

I claim:

1. In a catalytic process for converting hydrocarboncontaining oils by catalytic cracking followed by HP alkylation to more valuable products and for increasing the octane number of the gasoline products produced which comprises (a) introducing into and admixing with the hydrocarbon oil feed an octane improving amount in the range 0.1-18 weight percent of the hydrocarbon oil feed of a butene-l enriched normally gaseous butylenes fraction wherein butene-l is the major proportion of the butylenes fraction prior to contacting with the catalyst employed in the process, (b) charging the hydrocarbon oil feed together with said butylenes fraction to a catalytic cracking zone to convert the hydrocarbon oil feed into gaseous products comprising olefins including isomeric butene-2 formed by double bond isomerization from said butene-l, (c) recovering an olefin fraction containing said isomeric butene-2 from the gaseous fraction obtained from said catalytic cracking, and (d) charging said olefin fraction containing increased amounts of butene-Z to a zone for an HF alkylation of an isoparafiin with said olefins to form an alkylate product of increased octane number.

2. A process according to claim 1 wherein said normally gaseous butylenes fraction is admixed with hydrocarbon oil and then the admixture charged to a catalytic cracking zone using a silica-alumina catalyst in step (b) to maximize butene-2 production by double bond isomerization of butene-l with minimum loss of butenes to cracking and hydrogenation and a butylenes fraction is recovered in step (c) from said catalytic cracking zone and alkylated with isobutane to form a high octane alkylate of increased octane number in step (d).

3. A process according to claim 2 wherein the normally gaseous olefin is a high purity butene-l stream containing -95 percent butene-l which is blended with a hydrocarbon gas oil feed to the catalytic cracking operation prior to contact with hot cracking catalyst.

References Cited UNITED STATES PATENTS 2,326,553 8/1943 Munday 208128 2,425,482 8/ 1947 Moser 208 3,248,316 4/1966 Barger et a1. 2081 11 2,999,061 9/1961 Parsyn 20867 DELBERT E. GANTZ, Primary Examiner A. RIMENS, Assistant Examiner US. Cl. X.R. 

